The invention relates to a dragee-making apparatus which includes a rotating drum having an axis of rotation which is at least approximately horizontal.
In dragee-making drums, the dragee-making material such as granules, pellets, tablets or seeds is given one or more coatings by a liquid coating compound. The compound is sprayed onto or into the dragee-making material while the material is maintained in motion by the rotating dragee-making drum. The aim in so doing is for coatings of uniform nature, above all uniform thickness and density, to be formed on all the particles of the dragee-making material. These properties are of significance in, for example, such orally administrable medicaments as have to be resistant against gastric juices so as to release their active substances not before reaching the intestines.
The probability of uniform coatings being formed on all the particles of the dragee-making material is maximized if and when the separate particles roll over one another in regular succession as the dragee-making drum rotates. It hence has to be ensured that the separate particles of the dragee-making material are entrained substantially uniformly a certain distance upwards by the rotating drum and are then released to spill back down again.
Dragee-making drums of the kind described at the outset are known, for instance, from U.S. Pat. No. 3,874,092, in which a cylindrical shell is adjoined at either end by an end wall portion tapering frustum-shaped axially towards the outside. In such dragee-making drums, the dragee-making material is generally set into motion with sufficient force, yet in a way not damaging it too much, only if the inner surface of the shell is formed with baffle plates preventing the dragee-making material from sliding down the inner surface of the shell, even when the dragee-making drum is rotating at moderate speed. However, such baffle plates can be a considerable hindrance in cleaning the dragee-making drum, especially if they are of a varied shape or arrangement for promoting the thorough mixture of the dragee-making material.
The equivalent also applies to spherical or bulbiform dragee-making drums, as are likewise known from U.S. Pat. No. 3,874,092.